As background, people suffer from either Type I or Type II diabetes in which the sugar level in the blood is not properly regulated by the body. Many of these people may use a continuous glucose monitoring (CGM) to monitor their glucose level on an ongoing basis. In order to perform CGM, a glucose sensor may be placed under the skin which is capable of measuring the glucose level of the person in the interstitial fluid. The glucose sensor may periodically measure the glucose level of the person at a known time interval, such as every one minute, and transmit the results of the glucose measurement result to an insulin pump, blood glucose meter, smart phone or other electronic monitor.
In some cases, the measured glucose results (from the glucose sensor) may not accurately represent the glucose concentration. The glucose sensor may malfunction from time to time, such that the measured glucose results (from the glucose sensor) may be substantially different than the actual glucose level of the person. The glucose sensor may malfunction in this manner due to, for example, failure of the sensor electronics or battery or due to sensor “dropout.” Sensor dropout may occur due to physiological problems with the glucose sensor's attachment to the person, such as movement of the sensor relative to the person. Sensor dropout may cause the measured glucose results “drop” to near zero, although the actual glucose level of the person may be much higher. Additionally, the calibration of the glucose sensor may drift resulting in a bias toward greater than the true current blood glucose level or less than the true current blood glucose level. The glucose sensor may also experience an error which causes the CGM to no longer response to changes in the true blood glucose level and remain at an incorrect artificially high or artificially low blood glucose reading. Finally, a glucose sensor may be in the first day of use and have error in blood glucose measurement until stabilization.
As a result, embodiments of the present disclosure may process the measured glucose results from the person such that the actual glucose level of the person may be estimated, even in the presence of sensor noise and/or sensor malfunction. In addition, the future glucose level of the person may be predicted, based on the estimated glucose level.
As a result, embodiments of the present disclosure may implement an aggressiveness parameter in adjusting basal insulin rates to account for glucose sensor error.